What is alum used for?

Long-Haired Hare

We're trying another crystal project from About.com, growing giant crystals of alum. Alum -- or hydrated aluminum potassium sulfate, KAl(SO₄)₂^.12H₂O -- is sold in outrageously expensive little containers with the spices. It's used to make pickles crispy.

The kids wanted to know more, so we looked it up on Wikipedia.

You'll find alum in styptic pencils to staunch the bleeding from shaving, and underarm deodorant, because of both its antibacterial and anti-wetness properties.

Oh, and it's an astringent, which is why they can use it in Looney Toons cartoons to shrink heads. And you thought the only thing kids learned from watching Bugs Bunny was classical music!